Infrared single wavelength gas composition monitoring for metalorganic vapour-phase epitaxy

We discuss the use of fixed wavelength infrared absorption measurements as a means for observing compositional changes in MOVPE process gas mixtures u sing relatively simple instrumentation consisting of an incandescent lamp, a narrow bandpass filter matched to the CH stretch modes of the alkyl precu rsors, and an infrared detector. An advantage of this setup is that the low energy of the infrared radiation does not induce photolysis reactions on t he analyser cell windows in contrast to ultraviolet-based techniques. We pr esent preliminary data on gas composition measurements obtained in the alky l lines of an MOVPE reactor and show that useful information can readily be obtained on absolute gas concentrations, gas switching transients, and rea ctor line memory effects. (C) 2000 Elsevier Science B.V. All rights reserve d.